Electrical motors, such as actuator motors used in automotive applications, typically include a metal pole housing configured to receive magnets and an armature to form the electric motor. These metal pole housings are used to maintain a magnetic circuit of the electric motor in a closed field or loop manner. Therefore, the motor operates by having the armature turn inside the pole housing when a voltage is supplied to the motor. When an electric motor is energized, the armature rotates because wires on the armature are arranged relative to the magnetic field so that torque is developed about an axis of rotation of the armature. The armature includes a shaft having a first end portion which extends into a nose of the pole housing. The armature shaft also includes a second end portion which extends into a gear box. In order to support the rotating armature, first and second bushings are typically used on the first and second end portions, respectively, of the armature shaft.
Metal pole housings are produced using a variety of different manufacturing processes. For example, the pole housings may be formed by a deep drawn stamping process, a rolling process, an extrusion process, or other forming process. The cost of an electric motor changes significantly depending upon the type of manufacturing process used for the metal pole housings.
Typically, a deep drawn stamping process is used to manufacture metal motor pole housings for applications where water sealing is required. Deep drawn metal stamping processes are specialized and sophisticated. Therefore, few suppliers are able to meet an established stringent engineering requirement. As a result, product design and tooling costs are high for such deep drawn metal stamping designs. In addition, the material used in the deep drawn stamping processes is much more expensive than the material used in a rolled metal process.
Rolled metal pole housings are often used for electric motors where water sealing is not a requirement. Since the rolling or forming process is a relatively simple process, design and tooling costs are much less than those associated with the deep drawn stamping processes. Rolled pole housings advantageously have an outer wall with a uniform thickness. Rolled pole housings may also be made in varying lengths without a change in tooling which would be required in the deep drawn stamping process. However, conventional pole housings made using the rolling process are not water tight. Therefore, such conventional rolled pole housings are used for unsealed applications.
The present invention also provides an improved rolled pole housing which meets water sealing requirements. The present invention provides significant costs advantages, especially compared to deep drawn metal stamping processes.
According to an illustrated embodiment of the present invention, a pole housing for an electric motor comprises a frame body formed from a sheet of material. The frame body has a first end, a second end, and at least one seam. The seam is sealed along its length. The pole housing also includes a flange formed from a sheet of material, the flange having an opening formed therein. An entire periphery of the first end of the frame body is sealed to the flange. The pole housing further includes an end cap formed from a sheet of material. The end cap has a nose configured to receive an end of an armature shaft therein. The end cap is coupled to the second end of the frame body and sealed thereto to provide a sealed enclosure.
In an illustrated embodiment, the frame body is formed from a single sheet of material having first and second tabs extending from the first end. The first and second tabs are configured to enter first and second notches, respectively, formed in the flange to hold the frame body in position relative to the flange.
According to an illustrated embodiment of the present invention, a method of making a pole housing for an electric motor comprises forming a frame body from a sheet of material, forming a flange from a sheet of material, and forming an end cap from a sheet of material. The frame body has a first end, a second end and at least one seam. The flange has an opening therein, and the end cap includes a nose configured to receive an end of an armature shaft of an electric motor therein. The illustrated method also includes placing the flange adjacent the first end of the frame body, placing the end cap adjacent the second end of the frame body, sealing the at least one seam of the frame body, sealing the flange to the first end of the frame body, and sealing the end cap to the second end of the frame body to form a sealed enclosure.
In one illustrated embodiment, the sealing steps are performed using a laser welding process. Also in one illustrated embodiment, the steps of placing the flange adjacent the first end of the frame body and placing the end cap adjacent the second end of the frame body occur prior to the sealing steps.
In an illustrated embodiment, the end cap and the flange are formed from a single blank of material. Illustratively, the nose of the end cap is formed from the single blank of material leaving a large, flat flange attached. The flange of the pole housing is then cut from the large, flat flange attached to the end cap.
Additional features of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of illustrative embodiments exemplifying the best mode of carrying out the invention as presently perceived.